Most eukaryotic cell types, especially primary cells derived from soft tissues are exquisitely sensitive to changes in the physical properties of their substrates even when their chemical environment is held constant. In particular, some cells can sense the rigidity of their surrounding extracellular matrix (ECM) through a process which has been termed durosensing. Many studies now report strong cellular responses to substrate stiffness, but it remains unclear how cells measure rigidity and convert mechanical cues into biochemical signals. Delineation of the magnitude of stiffness to which different cells respond, and identification of essential roles for several proteins involved in formation of focal adhesion sites has laid the groundwork for defining how cells transmit forces and transduce them to the chemical signals at sites proximal or distal to the site of force application at the cell/substrate interface. This competitive revision proposes to expand the scope of work in the project R01GM083272 entitled "Mechanical control of cell growth and differentiation" that is directed at understanding cellular mechanosensing. Aim 1 of this revision builds on preliminary studies for a project to identify the physical and molecular details of the mechanisms by which cells measure substrate stiffness. Aim 2 is designed to develop and test a new generation of models to account for the elasticity of networks formed by filaments with the unusually large length, stiffness, and connectivity of biopolymers. Development of a theory for cytoskeletal and ECM mechanics, enabled by the work proposed in this revision and tested by the data generated in the parent project, has the potential to produce important design principles for new biomimetic materials. Successful outcome of this project would help define the mechanisms of mechanical signaling at the same level of detail as that of signaling by chemical stimuli, and might lead to physics-based therapeutic interventions in such settings as fibrosis, tumor growth and impaired wound healing. PUBLIC HEALTH RELEVANCE: NOT-OD-09-058 NIH Announces the availability of recovery act funds for competitive revision applications Attached are the required documents requesting a competitive supplement to my 5 R01 GM083272-02 titled "Mechanical control of cell growth and differentiation." I am requesting additional funds in the amount of $173,250 ($110,000 directs) for two employees both as a retention where these current positions will end if not funded plus a few supplies to perform additional/enhanced research aims defined in the proposal.